1. Field of the Invention
The present invention relates to heat exchange technology and, in particular, relates to an improved sealing component that may be used to reduce leakage between a hot gas conduit and a cold air conduit of a regenerative heat exchanging system.
2. Description of the Related Art
Conventional regenerative heat exchangers are used to provide preheated air to heavy machinery, such as a fuel burning power plant, and may be used with various types of machinery that exhaust hot gas and operate more efficiently when supplied with preheated air, such as, for example, chemical processors, refineries, pulp and paper mills, and ships. Typically, two fluid stream passages extend through the heat exchanger. The first passage may include a hot gas conduit that communicates with a hot exhaust outlet of the power plant. Hot exhaust gases flow from the power plant exhaust into the hot gas conduit of the heat exchanger. The second passage may include a cold air conduit that communicates with a cool air intake passage of the power plant. Cold air conduit feeds pressurized air into the intake passage of the power plant. As is known in the art, regenerative heat exchangers extract heat from the exhaust gases of the fuel burning power plant and transfer the heat to the cool air conduit.
As is also known in the art, leakage between the hot gas conduit and the cold air conduit reduces the thermal efficiency of heat exchangers. It is therefore desirable to provide a sealing mechanism between hot and cold conduits so that gas does not leak between the hot gas conduit and the cold air conduit. Therefore, seals may be mounted at the junctions between the movable heat exchanging body and the housing of the heat exchanging apparatus. Unfortunately, conventional seals have many disadvantages. For example, seals are typically exposed to harsh operating conditions, such as erosive fly ash and soot. As the heat exchanging body moves with respect to the housing or vice versa, the seals are also exposed to mechanical abuse because the seals are positioned to maintain sliding contact with the sealing surfaces. Consequently, the seals wear down quickly.
Further, the high operating temperatures of the heat exchanging apparatus expose the seals to thermal stresses which often cause the seals to warp. The high operating temperature also causes thermal distortions in the shape of the structural members of the heat exchanging apparatus, such as the housing and center shaft. The distortions in the shape of the seals and the structural members affect the clearance between the seals and the sealing surfaces, often resulting in leakage paths between the hot gas conduit and the cold air conduit. Such leakage paths typically reduce the thermal efficiency of the heat exchanging apparatus and also reduce the overall efficiency of the system.
Conventional seal designs do not adequately address these problems. Some seals are made from relatively thick metal which holds up well against corrosion and mechanical abuse. However, such seals are not very flexible and often lose contact with the sealing surface when the structural members of the heat exchanging apparatus thermally distort. Other seals are extremely flexible so that they initially offer better sealing characteristics by expanding or contracting when the structural members thermally distort to maintain contact with the sealing surface. However, such seals hold up poorly to corrosion and mechanical abuse.
Certain prior art seals have been equipped with flexible portions that allow the seal to flex in response to deformations in the heat exchanger. For instance, U.S. Pat. No. 5,950,707 discloses a seal having resilient components that allow for flexible deformations. However, such seals may fracture during excessive torque loads when exposed to very high differential pressures. As a result, stress fractures may allow gas leakage between conduits.
Additionally, flexible seals are sometimes subjected to excessive preloading during installation, causing increased stress on the seal during operation, which can shorten the life of the seal.
Therefore, there exists a need for an improved resilient seal that can be used in conjunction with heat exchanging systems to reduce the adverse effects of rotational stress loads, and certain applications with additional stress caused by high differential pressures, so as to substantially reduce the likelihood of leakage between hot and cold conduits of the heat exchanger, as well as that can inhibit the over-flexing of the seal during installation and operation of the heat exchanging system.